cells arise from other cells Flashcards

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1
Q

state what the cell cycle is and outline stages

A

cycle of division with intermediate growth periods
1. interphase
2. mitosis or meiosis
3. cytokinesis

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2
Q

explain why the cell cycle does not occur in some cells

A

after differentiation, some types of cell in multicellular organisms no longer have the ability to divide

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3
Q

what is the difference between the cell cycle and mitosis

A

cell cycle includes growth period between divisions; mitosis is only 10% of the cycle and refers only to nuclear division

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4
Q

outline what happens during interphase

A

G1: cell synthesises proteins for replication e.g. tubulin for spindle fibres and cell size doubles

S: DNA replicates = chromosomes consist of 2 sister chromatids joined at a chromatid

G2: organelles divide

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5
Q

state the purpose of mitosis

A

produces 2 genetically identical daughter cells for growth, cell replacement, tissue repair and asexual reproduction

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6
Q

name the stages of mitosis

A

prophase
metaphase
anaphase
telophase

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7
Q

outline what happens during prophase

A
  1. chromosomes condense, becoming visible (X-shaped: 2 sister chromatids joined at centromere)
  2. centrioles move to opposite poles of cell and mitotic spindle fibres form
  3. nuclear envelope and nucleolus break down = chromosomes free in cytoplasm
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8
Q

outline what happens during metaphase

A

sister chromatids line up at cell equator attached to the mitotic spindle by their centromeres

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9
Q

outline what happens during anaphase

A

requires energy from ATP hydrolysis

  1. spindle fibres contact = centromeres divide
  2. sister chromatids separate into 2 distinct chromosomes and are pulled to opposite poles of cell
  3. spindle fibres break down
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10
Q

outline what happens during telophase

A
  1. chromosomes decondense, becoming invisible again
  2. new nuclear envelopes form around each set of chromosomes = 2 new nuclei, each with 1 copy of each chromosome
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11
Q

explain the procedure for a root tip squash experiment

A
  1. prepare a temporary mount of root tissue
  2. focus an optical microscope on the slide. count total number of cells in the field of view and number of cells in a stage of mitosis
  3. calculate mitotic index (proportion of cells undergoing mitosis)
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12
Q

explain how to prepare temporary root tip mount

A
  1. place root in hydrochloric acid to halt cell division and hydrolyse middle lamella
  2. stain root tip with a dye that binds to chromosomes
  3. macerate tissue in water using mounted needle
  4. use mounted needle at 45 degrees to press down coverslip and obtain a single layer of cells. avoid trapping air bubbles
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13
Q

name 2 dyes that bind to chromosomes

A

toluidine blue (blue)

acetic orcein (purple-red)

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14
Q

why is only the root tip used when calculating a mitotic index

A
  • meristematic cells at root tip are actively undergoing mitosis
  • cells further from root tip are elongating rather than dividing
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15
Q

what are tumour suppressor genes

A

genes that code for proteins to trigger apoptosis / slow cell cycle

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16
Q

what are proto-oncogenes

A

genes that code for proteins to stimulate cell cycle to progress from one stage to the next

17
Q

how can mutation to tumour suppressor genes and proto-oncogenes cause cancer

A
  • tumour suppressor - no production of a protein needed to slow cell cycle
  • proto-oncogenes - form permanently-activated oncogenes
  • disruption to cell cycle - uncontrolled cell division = tumour
18
Q

suggest how cancer treatments control rate of cell division

A

disrupt cell cycle:
- prevent dna replication
- disrupt spindle formation = inhibit metaphase / anaphase

can also damage healthy cells

19
Q

how do prokaryotic cells replicate

A

binary fission

  1. dna loop replicates, both copies stay attached to cell membrane, plasmids replicate in cytoplasm
  2. cell elongates, separating the 2 dna loops
  3. cell membrane contracts and septum forms
  4. cell splits into 2 identical progeny cells, each with 1 copy of the dna loop but a variable number of plasmids
20
Q

why are viruses classified as non-living

A

they are cellular: no cytoplasm, no metabolism and cannot self replicate

21
Q

outline how viruses replicate

A
  1. attachment proteins attach to receptors on host cell membrane
  2. enveloped viruses fuse with cell membrane or move in via endocytosis and release dna/rna into cytoplasm or viruses inject dna/rna
  3. host cell uses viral genetic information to synthesise new viral proteins/nucleic acid
  4. components of new viral particle assemble
22
Q

how do new viral particles leave the host cell

A

a) bud off and use cell membrane to form envelope
b) cause lysis of host cell